docs: def create_destination(flowable, container, at_top_of_container=False):
      """Create a destination anchor in the `container` to direct links to
      `flowable` to."""
      vertical_position = 0 if at_top_of_container else container.cursor
      ids = flowable.get_ids(container.document)
      destination = NamedDestination(*(str(id) for id in ids))
      container.canvas.annotate(destination, 0, vertical_position,
                                container.width, None)
      container.document.register_page_reference(container.page, flowable)